"...insist that you believe Dorsai! is the best novel of military SF ever written: one could make a pretty good case for Heinlein’s Starship Troopers. I will, however, insist that those two-novels (first published within weeks of one another in 1959) are in combination the standard against which the subgenre of military SF must be judged."Notice that these two novels were published in the same year, almost within the same month. In fact, 1959-60 marked the debut of a number of military SF (mil-SF) novels that have since been recognized as classics. Vonnegut's Sirens of Titan, for example, and Pat Frank's Alas! Babylon were also published in 1959, with Walter M. Miller's A Canticle for Liebowitz following in 1960.
Mil-SF novels before Dorsai! and Starship Troopers were concerned with one of two themes: alien invasion or post-nuclear-war battles. These two novels introduced a new theme to mil-SF: the future soldier.
The novel Dorsai! started life as The Genetic General, and the name is apropos, since it serves as the opening for Dickson's sweeping saga of the perfectibility of Man. All ten or so books of the Childe Cycle share this concept: that Mankind can act to perfect its individual members. As told in Dorsai!, one path to perfection results in a personality born to command, with an instinctual grasp of the arts of war.
I might argue that the fourth book in the Cycle, Tactics of Mistake, is the most approachable presentation of Dickson's conception of the future soldier, in which he focused most explicitly on the future of conflict in the person of the commander, pre-Dorsai tactician-scholar Cletus Graeme. The tactics Graeme touts are equally applicable to ancient weapons and fighting techniques, like fencing, and this too is common with Dickson's future soldiers.
The protagonist of Dorsai!, Donal Graeme, is a descendant of Cletus Graeme, taking command of his contract-troops in a universe in which the fragmentation of the family of Man into septs—soldier, religious fanatic, Zen philosopher-mystics and physical scientists—is already well established.
Dickson was concerned with the personality, knowledge and warrior-abilities of the commanders. In his wars, individual soldiers, except where they impinge on the actions of the commanders, are sketchily drawn, as are the weapons of the future. We know they fight because they are contracted to do so; we never learn any more than that about their motivations.
Contrast this with the focus on the trooper in Heinlein's Starship Troopers. Veterans of battlefields from the US Civil War through current-day conflicts (and, I suspect, from Roman legions) would recognize the actions, attitudes, and behavior of the drop-troops Heinlein describes, even while the weapons and tactics they use in their battles are futuristic.
Here, the commander is an integral part of the troop, sharing in their attitudes and emotions, even while he possesses a broader picture of the conflict and the purpose of the battles they fight. Heinlein's future soldiers are fully human, not a fragment of humanity, and each fights for a reason other than his signature on a contract.
Just as he thought about where the future might lead with weapons development, Heinlein considered how the soldier of the future might change, and concluded that he would not. The "army of one" technology he describes for his space Marines does not isolate the trooper from his fellows; rather it tightens the esprit de corps of the troop by giving them an elite power.
There is much more in the novel than this conception of the future soldier, which makes Heinlein's Starship Troopers a much more interesting read than Dickson's Dorsai! New voting patterns in a one-world government, philosophy classes in high schools, levels of citizenship—these are all brought into the mix to support the central tale of the future soldier. But Heinlein's story centers around the starship troopers of the title, and that's appropriate.
You can read either of these books and enjoy the perspective of 1959 on the wars and soldiers of the future. Which direction will the future soldier take? Whether it is increasingly-perfected genetic powers, or increasingly powerful weapons carried by soldiers essentially unchanged since Thermopylae, there seems little doubt there will be war.
And thus there will be future soldiers.